Neurological complications of cardiac surgery: the need for new paradigms in prevention and treatment

Perioperative Care of the Patient with Eye Pathologies Undergoing Nonocular Surgery

The authors reviewed perioperative ocular complications and implications of ocular diseases during nonocular surgeries. Exposure keratopathy, the most common perioperative eye injury, is preventable. Ischemic optic neuropathy, the leading cause of perioperative blindness, has well-defined risk factors. The incidence of ischemic optic neuropathy after spine fusion, but not cardiac surgery, has been decreasing. Central retinal artery occlusion during spine fusion surgery can be prevented by protecting eyes from compression. Perioperative acute angle closure glaucoma is a vision-threatening emergency that can be successfully treated by rapid reduction of elevated intraocular pressure. Differential diagnoses of visual dysfunction in the perioperative period and treatments are detailed. Although glaucoma is increasingly prevalent and often questions arise concerning perioperative anesthetic management, evidence-based recommendations to guide safe anesthesia care in patients with glaucoma are currently lacking. Patients with low vision present challenges to the anesthesia provider that are becoming more common as the population ages.

Granulocyte colony stimulating factor reduces brain injury in a cardiopulmonary bypass-circulatory arrest model of ischemia in a newborn piglet

Ischemic brain injury continues to be of major concern in patients undergoing cardiopulmonary bypass (CPB) surgery for congenital heart disease. Striatum and hippocampus are particularly vulnerable to injury during these processes. Our hypothesis is that the neuronal injury resulting from CPB and the associated circulatory arrest can be at least partly ameliorated by pre-treatment with granulocyte colony stimulating factor (G-CSF). Fourteen male newborn piglets were assigned to three groups: deep hypothermic circulatory arrest (DHCA), DHCA with G-CSF, and sham-operated. The first two groups were placed on CPB, cooled to 18 °C, subjected to 60 min of DHCA, re-warmed and recovered for 8-9 h. At the end of experiment, the brains were perfused, fixed and cut into 10 µm transverse sections. Apoptotic cells were visualized by in situ DNA fragmentation assay (TUNEL), with the density of injured cells expressed as a mean number ± SD per mm(2). The number of injured cells in the striatum and CA1 and CA3 regions of the hippocampus increased significantly following DHCA. In the striatum, the increase was from 0.46 ± 0.37 to 3.67 ± 1.57 (p = 0.002); in the CA1, from 0.11 ± 0.19 to 5.16 ± 1.57 (p = 0.001), and in the CA3, from 0.28 ± 0.25 to 2.98 ± 1.82 (p = 0.040). Injection of G-CSF prior to bypass significantly reduced the number of injured cells in the striatum and CA1 region, by 51 and 37 %, respectively. In the CA3 region, injured cell density did not differ between the G-CSF and control group. In a model of hypoxic brain insult associated with CPB, G-CSF significantly reduces neuronal injury in brain regions important for cognitive functions, suggesting it can significantly improve neurological outcomes from procedures requiring DHCA.

Cytoprotective effects of the volatile anesthetic sevoflurane are highly dependent on timing and duration of sevoflurane conditioning: findings from a human, in-vitro hypoxia model

Using animal models, volatile anesthetics have been recognized for their neuroprotective effects. Nevertheless, there is still disagreement about the optimal duration and timing of conditioning with the volatile anesthetic sevoflurane in the human system. In the study presented, we employed a human neuronal cell culture model to investigate the effects of hypoxia and to evaluate potential cytoprotective properties of different sevoflurane conditioning strategies. Sevoflurane was applied to human IMR-32 cells in which hypoxic conditions were induced for 2h using our recently described two-enzyme model (Zitta et al., Eur. J. Pharmacol., 2010). Cellular effects of hypoxia and sevoflurane conditioning were evaluated by lactate dehydrogenase (LDH) measurements, brightfield microscopy, ELISAs, cytometric bead arrays, Westernblotting and RT-PCR. Hypoxia increased the release of LDH into the culture medium after 24h (normoxia: 0.15+/-0.02 a.u; hypoxia: 0.69+/-0.08 a.u, P<0.001) and expression of hypoxia associated genes HIF-1alpha, VEGF, catalase. Cytoprotective effects were observed in cultures that received sevoflurane for 30 min before hypoxia (preconditioning: 0.41+/-0.07 a.u., P<0.01) and for 30 min during the hypoxic period (intraconditioning: 0.20+/-0.01 a.u., P<0.001). Application of sevoflurane after the hypoxic insult did not lead to cytoprotection (postconditioning: 0.73+/-0.12a.u., P>0.05). Conditioning with sevoflurane for a total of 3h before, during and after hypoxia, however, resulted in an enhanced release of LDH (periconditioning: 0.97+/-0.10a.u., P<0.01) and additional cell damage. Hypoxia and sevoflurane intraconditioning were associated with changes in erk1/2 phosphorylation (T202/Y204) and HIF-1alpha protein levels, whereas phosphorylation of akt (S473) was not significantly altered. Our results suggest short pre- and intraconditioning with sevoflurane as most potent strategies to reduce hypoxia induced neuronal cell damage.

Using an automated emboli detection device in a porcine cardiopulmonary bypass (CPB) model: feasibility and considerations

The significant risk of cerebral embolism during cardiopulmonary bypass (CPB) makes monitoring of embolic events advisable already when developing new operation and coagulation management strategies for example in CPB animal models. The present study therefore evaluated in a porcine CPB model the feasibility of bilateral epicarotid Doppler signal recording and the quality of manual or automatic emboli detection. A total of 42 recordings (e.g. right carotid artery (n = 20), left carotid artery (n = 22)) were evaluated. The frequency of emboli counts was comparable for both carotid arteries. Automatic emboli detection, however, found significantly more embolic events per pig than did post-hoc manual off-line analysis of the recordings (172 +/- 217 vs. 13 +/-10). None of the brains, however, showed any emboli or infarction area either in cross-examination or in histological evaluation. In conclusion, the present study showed the feasibility of using an epicarotid Doppler device for bilateral emboli detection in a porcine CPB model. Automatic on-line emboli detection, however, reported more embolic events than did post hoc, off-line manual analysis. Possible reasons for this discrepancy are discussed.

Drug-induced methaemoglobinaemia following elective coronary artery bypass grafting

Dapsone can alter the oxygen carrying capacity of haemoglobin. Some patients are more susceptible to these effects because of genetic factors, comorbidities or peri-operative factors such as anaemia. We present a 57-year-old lady who underwent elective coronary artery bypass grafting. Deterioration in neurological and respiratory condition prompted a review of her drug treatment. A combination of long-term dapsone therapy, co-existing cardiac and respiratory disease, postoperative anaemia and renal impairment contributed to her decompensation, despite a relatively low level of methaemoglobin. Successful management included stopping dapsone therapy, supportive care and administration of ascorbic acid.

[Neurological complications in cardiac surgery post-operative period]

The incidence of neurological complications after cardiac surgery continues to be elevated, although this is variable in the different studies published, fundamentally because of the different populations studied and the different definitions of neurological dysfunction. The etiology of these alterations is attributed to a multifactorial origin, aortic artherosclerosis, cerebral hypoperfusion and inflammatory phenomenon secondary to the technique. This review arises from the recognition of the personal, economic, and socio-health care repercussion entailed by these complications, with high rates of mortality and morbidity recorded, and it tries to give an objective view of the current literature on the subject. Having knowledge of the risk markers and understanding the pathogenesis is important to try to plan strategies that may minimize the appearance and development of these complications and contribute to the decrease of their serious consequences. The data and the experience obtained by our group are shown at the end of the review.

Atherosclerosis of the ascending aorta as a major determinant of the outcome of cardiac surgery

Epiaortic ultrasonography has high sensitivity for the detection of atherosclerosis. In several studies, the technique has identified atherosclerosis of the ascending aorta as the major risk factor for stroke after cardiac surgery. The level of risk depends on the presence, location and extent of disease when the ascending aorta is surgically manipulated. This knowledge enables clinicians to focus on the diagnostic and surgical technique and to consider the various options. Routine use of intraoperative epiaortic ultrasonography should be applied so that surgical manipulation of the ascending aorta can be reduced or, if possible, avoided in patients with atherosclerosis of the ascending aorta. Alternatively, if major manipulation such as clamping must be performed in the presence of severe atherosclerosis, the use of intra-aortic filters could be considered.

Rehabilitation of postcardiac surgery stroke patients. Progress, outcomes, and comparisons with other stroke patients

OBJECTIVE

To examine the demographics, progress, and functional outcomes of all postcardiac surgery stroke patients admitted to the rehabilitation unit of an acute, tertiary general hospital over a 5-yr period and to compare this cohort with an age-matched control group of other stroke patients admitted during the same period.

DESIGN

A retrospective chart review of 47 postcardiac surgery stroke and a matched control group of other stroke patients admitted to the rehabilitation unit.

RESULTS

The mean age of the postcardiac surgery stroke patients was 70.80 +/- 8.37 yr, with 60% of patients being male. Their average length of stay on the rehabilitation unit was 15.64 +/- 11.96 days. Mean admit FIM total score was 65.64 +/- 16.33, with a discharge FIM total score of 86.77 +/- 18.93. Mean admit FIM motor score was 41.47 +/- 9.45, with a discharge FIM motor of 60.74 +/- 13.20. The other stroke group had significantly greater admit FIM total (P = 0.03), admit motor (P = 0.001), and discharge motor (P = 0.025) scores. FIM efficiency and motor and cognitive gains were comparable between the two groups. Length of stay on the rehabilitation unit was approximately 2 days less (P = 0.224) for the other stroke cohort. Ultimately, 39 (83%) of the postcardiac surgery stroke patients were discharged to the community compared with 45 (96%) of the other stroke patients (P = 0.19).

CONCLUSIONS

The majority of postcardiac surgery stroke patients successfully completed a comprehensive inpatient rehabilitation program. They had lower admit FIM total scores and admit and discharge FIM motor scores than the other stroke group and were almost as likely to ultimately return to the community.

Effects of intrathecal administration of a cell permeant caspase inhibitor, boc-D-fluoromethylketone (BDFMK), on behavioral deficits following spinal cord ischemia: a dose-response analysis

Caspase inhibition has been proposed as a target to attenuate ischemia-induced neurodegeneration and behavioral dysfunction. The present study evaluated the pharmacological effects of a single dose of an irreversible cell permeant general (nonselective) caspase inhibitor, Boc-D-fluoromethylketone (BDFMK) administered intrathecally (i.t.) in a reversible spinal cord ischemia model (RSCIM). Quantal analysis indicated that the P(50) (represents the duration of ischemia that produces permanent paraplegia in 50% of the animals in a group) of the control group was 25.08+/-4.71 min. Using the RSCIM, neuroprotection is observed if a drug significantly prolongs the P(50) compared to the control group. The P(50) values for the BDFMK-treated groups were 27.21+/-2.62, 27.28+/-3.29 and 28.98+/-2.32 min, for the three dose groups studied. There were no statistically significant changes when measured 18 or 48 h following ischemia. Biochemical analysis of cell extracts from the caudal lumbar spinal cord indicated that there was increased production of the 120-kDa fragment of fodrin suggesting enhanced caspase-3 activity, an increase that was reduced by i.t. BDFMK administration. Moreover, in caudal lumbar spinal cord extracts from a set of paraplegic rabbits (25-50 min occlusion), we measured a 32-42% decrease of caspase-3 activity in BDFMK-treated rabbits. The present study shows that i.t. administration of BDFMK reduced caspase-3 activity, but the inhibition did not translate into a significant behavioral improvement. Our results suggest that administration of a single dose of the caspase inhibitor BDFMK is insufficient to attenuate ischemia-induced behavioral deficits following aortic occlusion.

Neurologic outcomes after coronary artery bypass grafting with and without cardiopulmonary bypass

Neurologic injury, in the form of either stroke or more subtle neurocognitive impairment, is a frequent and potentially devastating complication of coronary artery bypass grafting (CABG). The etiology of CABG-associated neurologic injury is likely multifactorial, with the phenomena of cerebral hypoperfusion and embolism being the major contributors. Several perioperative strategies have been developed in an effort to reduce the incidence of CABG-associated neurologic complications. Hypothermic cerebral perfusion, alpha stat acid-base management, and slow patient rewarming have been shown by several investigators to minimize adverse neurologic sequelae associated with the use of cardiopulmonary bypass. Performing CABG without cardiopulmonary bypass (off-pump CABG), meanwhile, has been shown to reduce the risk of perioperative stroke, especially in high-risk patients such as the elderly. Whether off-pump CABG reduces the incidence of less severe neurocognitive impairment has not yet been clearly established and merits further investigation in the form of large, multicenter, randomized trials. Other technical innovations, such as the use of sutureless and clampless aortic anastomotic devices, also may be able to further minimize the neurologic complications associated with CABG.

Stroke after cardiac surgery: short- and long-term outcomes

BACKGROUND

Stroke remains a devastating complication of cardiac surgery, but stroke prevention remains elusive. Evaluation of early and long-term clinical outcomes and brain-imaging findings may provide insight into stroke prognosis, etiology, and prevention.

METHODS

Five thousand nine hundred seventy-one cardiac surgery patients were prospectively studied for clinical evidence of stroke. Stroke and nonstroke patients were compared by early outcomes. Data collected for stroke patients included brain imaging results, long-term functional status, and survival. Outcome predictors were then determined.

RESULTS

Stroke was diagnosed in 214 (3.6%) patients. Brain imaging demonstrated acute infarction in 72%; embolic in 83%, and watershed in 24%. Survival for stroke patients was 67% at 1 year and 47% at 5 years. Independent predictors of survival were cerebral infarct type, creatinine elevation, cardiopulmonary bypass time, preoperative intensive care days, postoperative awakening time, and postoperative intensive care days. Long-term disability was moderate to severe in 69%.

CONCLUSIONS

Stroke after cardiac surgery has profound repercussions that are independently related to infarct type and clinical factors. These data are essential for clinical decision making and prognosis determination.

Neurological injury after surgery for ischemic heart disease: risk factors, outcome and role of metabolic interventions

OBJECTIVES

Neurological complication remains a feared and increasing problem in association with cardiac surgery. The aim of this study was to analyze risk factors for neurological complications in a cohort of patients in whom inotropes for weaning from cardiopulmonary bypass was gradually replaced by metabolic treatment.

METHODS

The records of 775 consecutive patients undergoing coronary artery bypass grafting (CABG) or combined CABG+valve procedures were examined. Forward stepwise multiple logistic regression analysis was used for statistical evaluation of independent risk factors.

RESULTS

The incidence of neurological injury was 1.8% in patients undergoing isolated CABG and 5.4% after combined CABG+valve procedures. After cross-validation multivariate analysis identified history of cerebrovascular disease, advanced age and aortic cross-clamp time as independent risk factors for postoperative cerebral complications. Chronic obstructive pulmonary disease and number of bypasses also emerged as risk factors in the primary analysis.

CONCLUSIONS

In general, markers for advanced atherosclerosis, with history of cerebrovascular disease as the most important, emerged as predictors for neurological injury. Although it did not enter the final risk model, the results also suggest that postoperative heart failure deserves further surveillance as a potential risk factor for neurological complications. However, no evidence for untoward neurological effects associated with glutamate or glucose-insulin-potassium treatment was found.